Field of the Invention
The present invention relates to a precious metal paste suitable for bonding a substrate and a semiconductor element.
Description of the Related Art
A brazing material is widely used for bonding of various members, such as die bonding of a semiconductor element to a substrate, and an AuSn-based brazing material which is a fluxless brazing material is generally used. In the case where various members are bonded by using a brazing material, a method in which, after arranging a pair of members to be bonded with a brazing material sandwiched therebetween, the brazing material is fused by heating to a temperature equal to or higher than a melting point (about 300° C. or higher) at which the brazing material is molten is known. However, a problem sometimes occurred, in which, when heating to such a high temperature, electrical properties are varied in a member such as a semiconductor element due to a thermal stress applied to the member after bonding.
For this reason, a material which can bond members by heating to as low a temperature as possible is desired instead of a brazing material. As such a material, for example, Patent Literature 1 discloses a silver paste containing a silver powder and an epoxy resin and capable of bonding at a relatively-low temperature such as 100 to 200° C. In addition, the present inventors provide, in Patent Literature 2, a gold paste containing a gold powder having a predetermined purity and particle diameter and an organic solvent.